1. Field of the Invention
The present invention relates to a composite high frequency component and a mobile communication apparatus including the same, and more particularly to a composite high frequency component which can be used in three different communication systems and a mobile communication apparatus including the same.
2. Description of the Related Art
At present, as a mobile communication apparatus, a triple band portable telephone has been proposed which can be operated in plural frequency bands, for example, DCS (Digital Cellular System) and PCS (Personal Communication Services) which can be operated in the 1.8 GHz band, and GSM (Global System for Mobile communications) operative in the 900 MHz band.
FIG. 6 is a block diagram showing an example of the front end portion of a prior art triple band portable telephone. In this case, DCS and PCS using the 1.8 GHz band are employed as the first and second communication systems operative at adjacent frequencies, GSM operative in the 900 MHz band is employed as the third communication system applicable at a different frequency from the first and second communication systems.
The front end portion of the triple band portable telephone is provided with an antenna 1, a diplexer 2, first through third switches 3 through 5 having three ports, and first and second filters 6 and 7. The diplexer 2 has the function of coupling a transmitting signal by DCS, PCS, or GSM in the case of transmitting, and distributing a receiving signal to DCS, PCS, or GSM in the case of receiving.
The first high frequency switch 3 switches the transmitting section side of DCS and PCS to the receiving section side of DCS and PCS and vice versa. The second high frequency switch 4 has the function of switching the receiving section Rxd side of DCS and the receiving section Rxp side of PCS and vice versa. The third high frequency switch 5 has the function of switching the transmitting section Txg side of GSM and the receiving section Rxg side thereof.
The first filter 6 has the function of passing a transmitting-receiving signal by DCS and PCS and attenuating second and third higher harmonics, and the second filter 7 functions in passing a transmitting-receiving signal by GSM and attenuating the third higher harmonic.
Hereinafter, the operation of a triple band portable telephone that operates by DSC will now be described. In the case of transmission, by connection of the transmitting section Txdp common to DCS and PCS by means of the first high frequency switch 3, a transmitting signal from the transmitting section Txdp is sent to the first filter 6. The transmitting signal that is passed through the first filter 6 is wave-associated in the diplexer 2 and sent through an antenna 1. In the case of receiving, a receiving signal received through the antenna 1 is separated into its component waves in the diplexer 2. The receiving signal from the antenna 1 is sent to the first filter 6 which is on the DCS and PCS side. With the first high frequency switch 3, the receiving section side is turned on so that the receiving signal passed through the first filter 6 is sent to the second high frequency switch 4. The receiving section Rxd of DCS is connected by means of the second high frequency switch 4, so that the receiving signal passed through the second high frequency switch 4 is sent to the receiving section Rxd of DCS. When PCS is used, the transmission and reception is achieved by a similar operation.
The case of GSM will now be described below. In the case of transmission, the transmitting section Txg is connected by means of the third high frequency switch 5, so that a transmitting signal from the transmitting section Txg is sent to the second filter 7. The transmitting signal passed through the second filter 7 is wave-associated in the diplexer 2 and sent through the antenna 1. In the case of receiving, a receiving signal received through the antenna 1 is wave-branched in the diplexer 2, and the receiving signal from the antenna 1 is sent to the second filter 7 which is on the GSM side. By connection of the receiving section Rxg by means of the third high frequency switch 5, the receiving signal passed through the second filter 7 is sent to the receiving section Rxg.
However, in the above-described prior art triple band portable telephone mobile communication apparatus, the two high frequency switches are provided on the first and second communication system side, where the systems are operative at adjacent frequencies. Accordingly, the insertion loss due to the two high frequency switches occurs in the receiving sections. Thus, a problem exists in that the insertion loss is increased.
Further, the area which is occupied by the high frequency switches is large, and the circuit substrate is voluminous. As a result, there is also a problem in that the size of the triple band portable telephone (mobile communication apparatus) is large.
To overcome the above described problems, one embodiment of the present invention provides a composite high frequency component, comprising: a front end portion comprising a first communication system and a second communication system operative at adjacent frequencies to each other and a third communication system operative at a frequency different from those of the first and second communication systems; a diplexer for coupling a transmitting signal from said first, second and third communication systems in the case of transmission and for distributing a receiving signal to said first, second and third communication systems in the case of reception; a first high frequency switch having four ports for separating into a transmitting section common to said first and second communication systems, a receiving section of said first communication system, and a receiving section of said second communication system; a second high frequency switch having three ports for separating into transmitting and receiving sections of said third communication system; a first filter for passing a transmitting-receiving signal by said first and second communication systems; and a second filter for passing a transmitting-receiving signal by said third communication system.
According to the above described structure and arrangement, the two high frequency switches, that is, the first high frequency switch having the four ports and the second high frequency switch having the three ports are included. Thus, only the first high frequency switch are provided in the receiving path for the first and second communication systems operative at adjacent frequencies. As a result, the insertion loss in the receiving sections is reduced.
The two high frequency switches included in the composite high frequency component can be formed of the five diodes. Thus, the composite high frequency component can be miniaturized and produced inexpensively.
In the above described composite high frequency component, the on-off of the first high frequency switch may be controlled with a first controlling power supply connected to the transmitting section side common to the first and second communication systems, a second controlling power supply connected to the receiving section side of the first communication system, and a third controlling power supply connected to the receiving section side of the second communication system; and the on-off of the second high frequency switch may be controlled with a fourth controlling power supply connected to the transmitting section side of the third communication system, and a fifth controlling power supply connected to the receiving section side of the third communication system.
According to the above described structure and arrangement, the on-off of the first high frequency switch is controlled by means of the first through third controlling power supplies, and the on-off of the second high frequency switch by means of the fourth and fifth controlling power supplies. Thus, in transmission by the first and second communication systems operative at adjacent frequencies, all the three diodes constituting the first high frequency switch having the four ports are turned on. Thus, the higher harmonic distortion of the composite high frequency component can be reduced.
In the above described composite high frequency component, the on-off of the first high frequency switch may be controlled with first and second controlling power supplies connected to two selected from the transmitting section side common to the first and second communication systems, the receiving section side of the first communication system, and the receiving section side of the second communication system; and the on-off of the second high frequency switch may be controlled with a third controlling power supply connected to one of the transmitting section side of the third communication system and the receiving section side of the third communication system.
According to the above described structure and arrangement, the on-off of the first high frequency switch is controlled by means of the first and second controlling power supplies, and the on-off of the second high frequency switch by means of the third controlling power supply. Accordingly, in receiving by either one of the first and second communication systems which are in the post-stage of the first high frequency switch, or in receiving by the third communication system which is in the post-stage of the second high frequency switch, the voltages applied to the first and second controlling power supplies provided for the first high frequency switch, and the voltage applied to the third controlling power supply provided for the second high frequency switch become 0V. As a result, the consumption current of the composite high frequency component can be reduced.
In the above described composite high frequency component, at least one of the first and second filters may be arranged in the post-stage on the transmitting section side of the first and second high frequency switches.
According to the above described structure and arrangement, at least one of the first and second filters is arranged in the post-stage, or on the transmitting section side, of the high frequency switch. Thus, the distortion of a transmitting signal caused by a high-power amplifier, can be attenuated. Thus, the insertion loss in the receiving sections can be improved.
In the above described composite high frequency component, the diplexer, the first and second high frequency switches, and the first and second filters may be integrated with a ceramic multi-layer substrate formed by laminating a plurality of ceramic sheet layers.
According to the above described structure and arrangement, the diplexer, the high frequency switches, and the filters, which constitute the composite high frequency component, are integrated into the ceramic multi-layer substrate formed by lamination of ceramic plural sheet layers. Accordingly, the matching-adjustment between the diplexer and the respective high frequency switches can be easily achieved. It is unnecessary to provide a matching circuit between the diplexer and the high frequency switches and between the high frequency switches and the filters.
Accordingly, since the number of elements can be reduced, the circuit substrate for forming a microwave circuit with plural signal paths can be miniaturized.
In the above described composite high frequency component, the diplexer may comprise a first inductance element, and a first capacitance element; the first high frequency switch may comprise a first switching element, a second inductance element, and a second capacitance element; the second high frequency switch may comprise a second switching element, a third inductance element, and a third capacitance element; the first filter may comprise a fourth inductance element and a fourth capacitance element; the second filter may comprise a fifth inductance element and a fifth capacitance element; and the first and second switching elements, the first through fifth inductance elements, and the first through fifth capacitance elements may be contained in or mounted onto the ceramic multi-layer substrate, and connected with a connecting means formed inside of the ceramic multi-layer substrate.
According to the above described structure and arrangement, the diplexer is composed of the first inductance elements and the first capacitance elements, each of the first through third high frequency switches of the first and second switching elements, the second inductance elements, and the second capacitance elements, each of the first ad second filters of the third inductance elements and the third capacitance elements. They are contained in or mounted onto the ceramic multi-layer substrate and connected with the connecting means. Thus, the composite high frequency component can be formed by use of one ceramic multi-layer substrate, and can be further miniaturized. In addition, the loss due to the wiring between its elements can be improved.
Further, with the wavelength shortening effects, the strip-line electrodes which become the respective inductance elements can be shortened. Thus, the insertion losses due to these strip-line electrodes can be improved. As a result, the composite high frequency component can be miniaturized, and the reduction of the loss can be realized.
Another preferred embodiment of the present invention provides a mobile communication apparatus including any one of the above described composite high frequency components.
The above described mobile communication apparatus includes the composite high frequency component of the present invention, which is small in size and has a low loss. Accordingly, the mobile communication apparatus having the composite high frequency component mounted thereto can be miniaturized and enjoy high quality operation.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.